1. Technical Field
A recirculation system is disclosed for multiple fluid dispensing and formulation machines wherein the fluids being dispensed have limited amounts of volatile organic compounds (VOCs) and therefore have the propensity to become non-homogeneous and clog the dispense valves. The recirculation system prevents the settling out of heavier materials such as pigments of a colorant or tint, improves the dispense accuracy and reduces the maintenance of the multiple fluid dispensing machines.
2. Description of the Related Art
Systems for dispensing a plurality of different fluids into a container are known. For example, systems for dispensing paint base materials and colorants into a paint container are known. These paint systems may use twenty or more different colorants to formulate a paint mixture. Each colorant is contained in a separate canister or package and may include its own dispensing pump. The colorants and the respective pumps may be disposed on a turntable or along one or more stationary horizontal rows. In a turntable system, the turntable is rotated so that the colorant to be dispensed is moved to a position above the container being filled. In designs using one or more horizontal rows, the container may be moved laterally to the appropriate colorant/pump or the colorants may be dispensed through a manifold.
In paint dispensing applications, precision is essential as the color formulations or paint formulations require the addition of precise amounts of tints or colorants so the chosen color of paint does not vary from container to container. One way in which the precision of a paint dispensing systems is compromised is a non-uniform condition of a colorant or tint caused by a settling out of heavier components of the colorant slurry during storage in the canister and prior to dispensing or between dispenses. Specifically, the actual pigments of colorant slurries tend to be heavier than the remaining components, such as the solvent. As these heavier materials gather or collect towards the bottom of the canister under the force of gravity, the colorant slurry has a non-uniform concentration from the bottom of the canister to the top of the canister. As a result, the heavier pigment materials may be dispensed in a higher concentration when the canister is relatively full and at a lower concentration when the canister is close to being empty. The non-uniformity of the colorant slurry leads to inaccuracies in the final paint formulation.
As a result, there is a need for an improved paint colorant or tint canister for use in automated paint dispensing machines that avoids this problem. Further, the above problems are exacerbated by European and California regulations that are becoming increasingly hostile to the use of volatile organic components (VOCs) in paints and paint colorants. VOCs are very effective solvents at maintaining colorants, pigments and other heavier materials in a uniform slurry. The elimination or restriction of VOCs reduces the time it takes for heavier materials to settle out of a slurry that needs to be uniform for accuracy purposes. For example, low-VOC or no-VOC paint pigments require frequent recirculation to ensure that the final formulation is accurately dispensed.